The present invention relates to printers, and more specifically, to apparatus and methods for printing on thermal paper using a thermal head.
Thermal printers are used for printing various documents including purchase receipts. The printers for the purchase receipts are used in point-of-sale (POS) and electronic cash register (ECR) stations. Today, some ECRs print images such as discount coupons on the purchase receipts with multiple colors, which attract more attention of the customers than a single color.
In the prior art, there are thermal printers that print on thermal paper in two colors (e.g., magenta and black) using two-color thermal paper. The two-color thermal paper is colored in magenta when relatively low heating energy is applied thereto, and is colored in black when relatively high heating energy is applied. However, the use of this two-color thermal paper poses some problems. For example, the cost of the two-color thermal paper is relatively high compared to mono-color thermal paper. A black dot printed on the two-color thermal paper often looks dark red or brown since the high heating energy for black color causes areas adjacent to the black dot to be heated to such an extent that the adjacent area is colored magenta. Furthermore, there is no way to print in more than two colors by using the two-color thermal paper.
In view of these and other issues, it would be desirable to have a technique allowing a thermal printer to print in two or more colors on thermal paper with high quality of images inexpensively.
According to various embodiments of the present invention, a combination printer has a direct thermal printing head and a thermal transfer printing head. The direct thermal printing head is positioned upstream relative to the thermal transfer printing head. Here, the energy necessary for the direct thermal printing is higher than the energy necessary for the thermal transfer printing. Thus, the downstream head for the thermal transfer printing does not deteriorate the printing quality by coloring thermal paper which is printed by the direct thermal printing upstream relative to the thermal transfer printing head.
In some embodiments, the printer further includes a first platen that serves as a back support for the thermal head, and a second platen that serves as a back support for the thermal transfer printing head. The first and second platens may be arranged to apply tension to the thermal paper therebetween.
In some specific embodiments, the second head is movable away from the paper flow path in a direction transverse to the thermal paper, and a transport mechanism is provided to support the thermal paper at least when the second head moves away from the paper flow path.
Still another aspect of the present invention provides a method for printing. The method includes printing on thermal paper by both heating, and printing ink on the thermal paper. In a specific embodiment, the printing ink on the thermal paper includes thermal transfer printing for transferring ink from an ink film to the thermal paper.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.